Instructions
This calculator will show you the effects of tolerance in cartridge alignment and will help you find an optimized geometry.
Perfection is extremely difficult to achieve when aligning a phono cartridge. Small angular and overhang errors are nearly impossible to see, even with a loupe.
The concept of considering the angular error is not entirely new, though it has never really caught on outside of Germany, where Walter E. Schön’s protractor has been one of the most popular alignment tools since the early 1980s. This alignment error calculator takes it one step further by considering the overhang error in addition to the error in offset angle.
The default error values should be a good starting point (though we currently cannot be sure how much alignment error is to be expected; it will most likely depend on the type of protractor one is using). Just enter the pivot to spindle distance, press 'Calculate' and it will show the distortion curve for a perfect alignment as well as eight grey curves for different alignment error scenarios. The blue dots show the highest distortion you may get at the outer groove, inner groove and at the highest point of the curve between the null points if the cartridge is misaligned within the specified tolerances.
As you can see, alignment error may cause a lot more distortion at the inner grooves than at the outer.
Now you can minimize the distortion by tweaking the locations of the inner null and outer null. The three maxima will need to be equally high. The dashed blue line is a visual aid that will make it easier to see at which point the maximum distortion needs to be lower or higher. As the calculator rounds the distortion to three decimal places, matching them to two decimal places is a reasonable goal.
Once you have found a good geometry, you may transfer the null points to one of the protractor generators.
Please note that the resulting null points are not universal. They will only compensate for the alignment error at a particular pivot to spindle distance.
Many thanks to Dr. Vladan Jovanovic, who discussed the issue of alignment error with me in great detail and was a great help in making this calculator possible. [ADVERTISEMENT: Make sure to check out his book 'Electronics of Rock and Roll']